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For many years Linux (RedHat then OpenSuse) was the primary operating system for my Webel consultancy, and Linux was crucial to my work with many scientific institutes and software engineering clients. Thankyou Linus et al !

I have used UNIX for well over 20 years (showing my age there), including variants such as: Linux, Mac OS X, Sun Solaris, SGI IRIX, HP-UX, IBM AIX, BSD and the UNIX-like Domain-OS, (given in no particular order of preference).